Device for lapping tap chasers



July 22, 1941.v

` H. M. JOHNSTON DEvIcE Foa LAPPING TAP cHAsERs Filed oct. 19, 1959 4 Sheets-Sheet 1 PIE- 1..

y /f JOHNSTON, j. C? I i@ July 22f1941- H. M. JOHNSTON 2,250,380

DEVICE FOR' LAPPING TAP cHAsERs f Filed oct. 19, i939 4 Sheets-Sheet 2 July 22,' l941 H. M. JoHNs-roN 2,250,380

' DEVICE FOR LAPPING TAP CHASERS I Filed oct. 19, 1939 4 sheets-sheet :5

JulylZZ, 1941. H. M. JoHNs-roN 252505380 DEVICE FOR LAPPING TAP CHASERS A Filed Oct. 19, 19.39- 4 Sheets-Sheet 4 Patented July 22, 1941 National Tube Company, a

Jersey corporation of New Application October 19, 1939, Serial No. 300,245

(KCl. 51--73) 13 Claims.

This invention relates to the lapping of tap chasers, and particularly to an improved method and device for lapping the same.

It is desirable in preparing circular tap chasers as used for lapping couplings for operating service, to form a flat surface or lap of about elf inch to ,-15 inch wide at an angle of about 45 degrees on the lead cutting edge of each tap chaser after the Chaser rake angle has been ground on each of them to restore the cutting edge and the proper thread form. This lap is necessary in order to stabilize the cutting action of the tap and to prevent chattering during the tapping operation. Without such a lap on the chasers it is necessary to commence operation of a new set of chasers at a reduced speed to avoid chattering and then gradually increasing the cutting speed as the chasers are broken in until the chattering completely disappears.

Heretofore, this nat surface or lap was formed on each individual tap Chaser manually by means of an abrasive stone. 'I'he forming of this at surface or lap on the chasers by hand was not only tedious but it was practically impossible to produce a uniform lap on each of a complete set of tap chasers so as to obtain a uniform cutting action of the Chaser lead and variable operating results were often obtained and consequently corrective measures were often necessary.

For instance, if the lead cutting edgevis not absolutely uniform on each of the chasers, the slight errors of the component tap parts supporting the chasers, if cumulative, will produce a variable radius of cutting diameter of the several chasers in the set and cause some chasers to remove more material than others, thus destroying the stability of the cutting action.

In the present invention, there is provided a method and device that laps the lead cutting edge of a complete set of chasers all atone time l to absolute uniformity. The complete set of tap chasers is lapped in the actual position they assume when in operating use and they are mounted on the identical chaser blocks that support the same during their use. Thus, it will be seen that any cumulative errors that affect the radius of the cutting edges of the'various tap chasers are automatically corrected in the lapping operation by the use of the device of the present invention; thereby eliminating the above named disadvantages. Furthermore, by lapping the tap chasers in the device in accordance with the present invention, the chasers not only can be started in operation at the maximum tapping speed without chattering, but they have a considerably increased life per grind.

Accordingly, it is one of the objects of the present invention to provide an improved method of and device for lapping tap chasers which laps a complete set of tap chasers all at one time and provides an efficient and uniform lap in each of them, thereby obtaining better operating results.

It is another object of the invention to provide an improved device for lapping tap chasers which is simple and inexpensive in its construction, and one that is easily maintained.

It is a further object of this invention to provide an improved method of and device for lapping tap chasers which is simple and convenient in its practice and use, and at the same time, one which quickly and effectively laps the chasers.`

Various other objects and advantages of this invention will be more apparent in the course of the following specification and will be particu.- larly pointed out in the appended claims.

In the accompanying drawings there is shown, for the purpose of illustration, vone embodiment which my invention may assume in practice.

In these drawings: Y

Figure 1 is a vertical section through the improved lapping device of my invention;

Figure 2 is a plan View thereof;

Figure 3l is a detail in plan showing the core member together with one of the chaser blocks in engagement therewith;

Figure 4 is an elevation of Figure 3; v Figure 5 is an end View of one of the slots in the nose piece;

Figure 6 is a detail in plan of one of the chaser blocksV together withv a tap chaser assembled thereon;

Figure 7 is an enlarged section showing the lapping of a tap Chaser;

Figure 8 is a view similar to Figure 2 showing the thread chaser positioned on the device; and

Figure 9 is a vertical section through Figure 8.

Referring more particularly to the drawings, the improved device of my invention comprises a cylindrical-shaped member 2, sometimes called a nose piece, having a hollow portion 3 arranged axially thereof. The cylindrical-shaped member 2 is vertically mounted preferably on a supporting or base member t an-d securely attached thereto by means of cap screws 5, and the base member 4 in turn is supported preferably by a plurality of leg members 6,

rIhere is arranged in the top surface .of the cylindrical-shaped member 2 and extending from the outer edge thereof inwardly to the hollow rality of vertically extending slots I4 equal in number to the number of slots 'I in the member 2 and oppositely disposed from the same. The slots I4 .are adapted to receive the L-shaped or hooked portion I5 arranged on the inner end of each of the chaser blocks 9 so as to be held in slidable engagement therewith, las shown in Figures 3 and 4. The core member I3 is securely mounted on the upper end `of an enlarged cylindrical headl or flange I6 of a vertically extending screw I'I also axially disposed in the hollow portion 3 of the cylindrical-shaped member 2 and securely attached thereto preferably by means of a cap screw I8. There is rotatably mounted below a cylindrical hole I9 arranged axially of the cylindrical-shaped member 2 below the hollow portion 3 thereof in the base member 4, a knurled adjusting nut 29, which is held in rotatable engagement therewith preferably by Ia keeper ring 2I disposed on the :top side of base 4 above the opening I9 therein with machine screws 22 interconnecting the same. The adjusting nut 29 cooperates with the screw I'I and supports the same together with the conicalshaped core member I3 arranged on the upper end thereof. There is preferably disposed above the keeper ring 2| around the screw II, a felt washer 23 or other suitable mean-s for protecting the threads of the screw and for lubricating the same together with the adjusting nut.

There is securely arranged around `the cylindrical-shaped member 2, an externally threaded annular member 24 having an internally threaded annular lsupporting member or elevating table 25 rotatably disposed therearound which is adapted to cooperate therewith to move the supporting member 25 vertically of the annular member 24. There is adjustably arranged circumferentially of the supporting member 25 and extending outwardly therefrom, a plurality of handles 26 for rotatably moving the same. On the inner wall of the supporting member 25 there is arranged therearound opposite the inner end-s of the handles 2G and next to the outer threaded portion of the annular member 24, an lannular pliable member 2'I. preferably made of leather or some other suitable material.

There is preferably disposed between the inner end of each of `the handles 25 and the annular pliable member 24, `a coil spring 28 for yieldably retaining the annular leather member against the outer threaded portion of the member 24. The inner ends of each of the handles are threaded yand cooperate with a threaded portion of the opening in the rotatable member 25 in which they are disposed so as to adjust the yieldableness of the coil spring 28. It is the purpose of the annular pliable member 24 to act as a brake so as to prevent the rotatable supporting member 25 from accidentally rotating on the annular member 24, as will be seen hereinafter.

There is adapted to be disposed above the cylindrical member 2, and the chaser blocks 9 together with the tap chasers IIJ carried thereby. an interchangeable annular lapping member 29 preferably made of cast-iron of a close grain structure. The annular lapping member 29 preferably has an angularly arranged inner surface 30 being arranged at the angle of the lap desired on the tap chasers, and which is charged with an abrasive material consisting preferably of a mixture of loose grain carborundum and olive oil or any other suitable abrasive. The lapping member 29 preferably has a plurality of downwardly extending leg members 3| arranged therearound which are adapted to rest on the rotatable supporting member or elevating table 25 for the purpose of stabilizing and 'aligning the lapping members 29 relative to the tap chasers during the lapping thereof. There is preferably arranged circumferentially of' the lapping member 29, a plurality of outwardly extending handles 32 for actuating ythe same as will be described.

To restore the lap angle to the lead cutting edge of each of a complete set of tap chasers as shown in Figures 1, 2 and '7 of the drawings, the device of the present invention fimctions in the following manner:

Each of a complete set of tap chasers I or the tap chasers to be lapped, is first assembled on the Chaser supporting blocks 9 with the lead cutting edge extending outwardly therefrom as shown in Figure 3 of the drawings and securely fixed thereon by means of the cap screws I2 to prevent the turning thereof. The conical-shaped member I3 is then moved so as to be telescopically arranged within the hollow cylindrical member 2 by turning the adjusting nut 20 so as to lower `the screw I'I on which .the conical-shaped member I3 is mounted. Each of the chaser supporting blocks 9 with the tap chasers I0 assembled ythereon is then mounted on the cylindrical member 2 with the T-shaped porti-ons 8 thereof slidably disposed within the slots 1 arranged in the top surface of the cylindrical member 2, as shown in Figure 5. The yconical-shaped member I3 is then moved upwardly by turning the adjusting nut 29 in the opposite direction and as the conical-shaped member I3 moves upwardly, the slots I4 carried thereby are engaged by the L-shaped or hooked-portions I5 arranged on the inner end of each of the chaser supporting blocks 9. The tap chasers are then adjusted radially of the cylindrical member 2 by further moving the conical-shaped member I3 upwardly due to the action of the screw I'I and the adjusting nut 20 until the tap chasers are properly positioned for the lapping operation.

The annular lapping member 29 is then positioned above the cylindrical member 2 over all of the tap chasers I'Ii with the inner angular surface 3D thereof contacting the upper portion of the lead cutting edge of each of them. The supporting or elevating table 25 is then adjusted so that the ends of the downwardly extending legs 3I rest thereon. The elevating table is then lowered so that there is a slight clearance between ne ends of the legs 3l and the top of the supporting table. The annular lapping member 29 is then manually rotated by means of the handles 32, carried thereby in a clockwise direction. As the lapping member 29 is rotated the lap angle 4I, as shown in Figure 7, is being restored to the lead cutting edge of each of the chasers all at one time. As the lapping operation continues,

the elevating or supporting table 25 is gradually lowered by means of the handles 25 so as to always maintain a slight clearance between the table and the ends of the legs 3l carried by the lapping member 29. It will be understood that the purpose of the elevating or supporting table 25 is to maintain the annular lapping member 29 in correct alignment with each of the tap chasers throughout the lapping operation so as to provide an even lap on each of the tap chasers by stabilizing the rotatable movement of the annular lapping member 29V.

It will be seen that the lap angle is less than the chaser lead angle relative to the horizontal, thereby providing a wider lapped surface at the outer end of the chaser lead cutting edge which gradually diminishes in the direction of the threaded portion of each of the chasers.l

In Figures 8 and 9 of the drawings, there is shown means interchangeable with the annular lapping member 29 for restoring the lap to the threaded portions of the tap chasers. Such means consists of an annular housing member 33 which is preferably U-shaped in cross section.

There is disposed within the annular housing member 33 a plurality of internaly threaded segmental members 34 which are movable radially therein and preferably held in slidable engagement therewith by means of a tongue and groove arrangement as at 35. rThere is arranged between each of the segmental members 3e and the outer wall of the anular housing member 33, a coil spring 35 which is adapted to yieldably retain the segmental members 34 in position therein. There is circumferentially arranged around the annular member 33 a plurality of outwardly extending handles 31 having their. inner ends threaded and disposed in threaded holes arranged in the periphery of the annular member 33. The inner end of each of the handles 31 bears against the outer end of the coil springs 33 and is arranged so as to adjust the yieldableness thereof. There is mounted on each of the segmental members 3d, an upwardly extending pin 38 which extends upwardly through a slotted opening 39 arranged in the top wall of the annular member 33 for the purpose of moving thesegmental members 34 manually of the member 33. There is arranged around the bottom side of the annular member 33 a plurality of downwardly extending f legs 40 which are adapted to rest on the elevating or supporting table 25 for the purpose of maintaining the annular member 33 in alignment.

It will be understood that after Vthe lap angle has been properly restored to the lead cutting i edge of the tap chasers by the annular lapping member 29, the annular lapping member 29 is removed from the top of the chasers and the annular thread lapping member 33 together with the segmental members 34 carried thereby is positioned thereon with the downwardly extending legs carried thereby resting on the elevating table 25. The handles 31 are then turned and adjusted so that the coil springs 36 force each of the segmental members 33 inwardly, whereby the threads on the inner surfaces thereof engage with the threads of the tap chasers. The supporting table 25 is then lowered as before so as to provide a slight clearance between the ends of the legs l0 and the table. The annular housing member 33 is then manually rotated, or power means may be provided if desired for turning the same and the lead cutting edge of each of the threads of the tap chasers as shown at 42 in Figure 9 is then being restored by the segmental members 34. The coil springs 36 maintain the segmental members in contact with the threads of the tap chasers as the lapping device moves upwardly over the taper of the chasers and the proper yieldableness of the coil springs 36 is adjusted by means of the handles 31. It will be seen that the segmental construction of the threaded lap permits the threaded lapping device to follow the helical path of the threads of the chasers.

After the lapping of the lead cutting edge of the threads of the chasers has been completed, the compression of the coil springs 36 against the segmental members 34 is relieved by turning the handles 31 and each of the segmental members 3E is outwardly moved to a retracted position away from the tap chasers and out/of engagement therewith by means of the upwardly extending pins 38 carried thereby. The elevating table 25 is then rotated by means of the handles 3l carried thereby so as to move the same upwardly which, in turn, moves the annular threaded lap ping member 33 to the top of the device and it is then removed from the top of the tap chasers.

The lapping of all of the chasers is new completed and they are then removed from the device by lowering the conical-shaped member i3 to its retracted position within the cylindrical member 2 by turning the knurled adjusting nut 23, which, in turn, moves the conical-shaped member i3 through the action of the screw I?. After the conical-shaped'member I3 has been moved to its retracted position within the cylindrical member 2, the L-shaped or hooked portions I5 and each of the chaser blocks 9 are disengaged from the slots i4 carried by the conical-shaped member and each of the chaser blocks together with the tap chasers i0 carried thereby is removed from the top of the cylindrical member 2 by sliding the chaser blocks radically outwardly so as to disengage the lower T-shaped portion carried thereby from the T-shaped slots i arranged in the top of the cylindrical member. The lapping operation of both the lap angle and the threads of each of the chasers is now completed and they are ready for use.

As a result of my invention, it will be seen that there is provided a simple and inexpensive method of and device for lapping tap chasers wherein both the lap angle and the lap on the threads are easily and quickly restored to the lead cutting edge of each of the chasers all at one time, thereby providing a uniform lapping on each of them.

While I have shown and described an embodiment of my invention, it will be understood that this embodiment is merely for the purpose of illustration and description and that various other forms may be devised within the scope of my invention, as defined in the appended claims.

I claim:

1. In a device of the class described, means for holding in a circular arrangement a plurality of tap chasers to be lapped, means for adjusting radially the positions of said tap chasers thereon, and rotatable means which is adapted to lap the lead cutting edge of each of the chasers all at one time upon rotation of said means.

v 2. In a device of the cl-ass described, a stationary cylindrical-shaped hollow supporting member, means arranged on said member for movably holding in a circular arrangement a plurality of tap chasers to be lapped, means arranged axially of said supporting member for moving and adjusting the position of said tap chasers radially thereon, and rotatable means adapted to be disposed above the supporting member whichis adapted to lap the lead cutting edge of each of the chasers all at one time upon rotation of said means.

3. In a device of the class described, means for holding in a circular arrangement a plurality of tap chasers to be lapped, means for adjusting radially the position of said tap chasers thereon, and a rotatable member on which there is adapted to be disposed an abrasive means which is adapted to lap the lead cutting edge of each oi the chasers all at one time upon rotation of said member.

4. In a device of the class described, means for holding in a circular arrangement a plurality of tap chasers to be lapped, means for adjusting the position of said tap chasers radially thereon, a rotatable member on which there is adapted to be disposed an abrasive means which is adapted to contact and lap the lead cutting edge of each of the chasers all at one time upon rotation of said member, and means for maintaining said rotatable member in proper position relative to said tap chasers during the lapping operation.

5. In a device of the class described, a stationary cylindrical-shaped hollow supporting member, means arranged on said member for movably holding in a circular arrangement a plurality of tap chasers to be lapped, means arranged axially of said supporting member for moving and adjusting the position of said tap chasers radially thereon, and a removable rotatable annular member adapted to be disposed above said supporting member in contact with the outer edges of said tap chasers, said annular member having an angularly arranged inner surface having abrasive means carried thereby which is adapted to lap the lead cutting edge of each of the chasers all at one time upon rotation thereof.

6. In a device of the class described as dened in claim 5 including an annular member adjustably arranged around said supporting member with which means carried by said rotatable annular member is adapted to cooperate to maintain the same in proper position relative to the tap chasers during the lapping thereof.

'7. In a device of the class described, a stationary oylindrical-shaped hollow supporting member, means arranged on said member for movably holding in a circular arrangement a plur-ality of tap chasers to be lapped, a conical-shaped member arranged axially within said supporting member for vertical movement therein which is adapted to move said tap chasers all at one time radially of said supporting member, means for moving and adjusting the position of said conical-shaped member vertically in said supporting member, and a removable rotatable annular member adapted to be disposed above said supporting member in contact with the outer edges of said tap chasers, said annular member having an angularly arranged inner surface having abrasive means carried thereby which is adapted to lap the lead cutting edge of each of the chasers all at one time upon rotation thereof.

8. In a device of the class described, a stationary cylindrical-shaped hollow supporting member, a plurality of chaser blocks each of which is adapted to support a tap ohaser, said Chaser blocks being circularly arranged on the top of said supporting member in radially movable engagement therewith, a conical-shaped member arranged axially within said supporting member for vertical movement therein, the inner end of each of said chaser blocks being movably interengaged with said conical-shaped member whereby any vertical movement thereof will mpart a radial movement to all of said Chaser blocks and ythe tap chasers carried thereby at one time, means for moving and adjusting the position of said conical-shaped member vertically of said supporting member, and a removable rotatable annular member adapted to be disposed above said supporting member in contact with the outer edges of said tap chasers, said annular member having an angularly arranged inner surface having abrasive means oarried thereby which is adapted to lap the lead cutting edge of each of the chasers all at one time upon rotation thereof.

9. In a device of the class described, as dened in claim 8 including an annular member adjustably arranged around said supporting member with which means carried by said rotatable annular member is adapted to cooperate to maintain the same in proper position relative to the tap chasers during the lapping thereof.

10. In a device of the class described as dened in claim 8 wherein the means for moving and adjusting the position of the conical-shaped member vertically in the supporting member consists of a screw member arranged axially of said supporting member and extending downwardly therethrough, said screw having the upper end thereof securely attached to the bottom of the conical-shaped member and an. adjusting nut mounted on the lower end thereof which is in rotatable engagement with the bottom of said supporting member.

11. In a device of the class described, means for holding in circular arrangement a plurality of tap chasers to be lapped, means for adjusting the position of said tap chasers radially thereon, a rotatable thread-lapping means, said threadlapping means adapted to lap the lead cutting edge of the threads of each of the chasers all at one time upon rotation of said means.

12. In a device of the class described as defined in claim 11 wherein the rotatable threadlapping means consists of an annular housing member having a plurality of internally threaded segmental members yieldably arranged therein.

13. In a device of the class described, a stationary cylindrical-shaped hollow supporting member, means arranged on said member for movably holding in a circular arrangement a plurality of tap chasers to be lapped, means arranged axially of said supporting member for moving and adjusting the position of said tap chasers all at one time radially of said supporting member, a rotatable annular housing member adapted to be disposed above sai-d supporting member, a plurality of internally threaded segmental members yieldably arranged within said annular housing member, said segmental members adapted to lap the lead cutting edge of the threads of each of the chasers all at one time upon rotation of said annular housing member and the segmental members carried thereby.

HARRY M. JOHNSTON. 

